We have been studying the molecular mechanisms by which HSV-1 activates HIV RNA transcription. Understanding the system could provide general insights into activation and clinical progression of HIV infection. We had shown previously that HSV stimulates HIV transcription in two distinct ways. Using transient expression assays in Jurkat cells with a CAT reporter we found that the bulk of HSV activation is dependant on the integrity of Spl and NF-KB enhancers upstream of the HIV transcription start site. During the past year we examined an alternative activation mechanism. By gel shift we showed that HSV induces a cellular protein(s) that binds near the HIV transcriptional start site. Competition experiments proved the binding specificity of the protein and uV-cross linking studies identified a novel 45kD protein. HSV-l rapidly and markedly upregulates levels of this protein. We are currently attempting to clone the protein, termed LBP-2, from a Jurkat cell cDNA library.